研究了Bi含量对Al-5Mg-2Si-0.6Mn 合金铸态组织、相结构和成分、力学性能和断口形貌的影响。 结果表 明，当Bi含量为0.3%时，具有最明显的变质效果。 Bi富集在共晶Mg2 Si生长界面前端产生成分过冷，减小了液相的实 际过冷度，使共晶Mg2 Si的生长速度被限制，共晶Mg2 Si相从变质前的粗纤维状转变成细小的点状纤维。 合金的力学性 能显著提高，抗拉强度、伸长率分别由未变质的205MPa、2.8%增加至240MPa、5.3%，分别增加了17.1%、89.3%。

 The effects of Bi content on the microstructure, phase structure and composition, mechanical properties and fracture morphology of as-cast Al-5Mg-2Si-0.6Mn alloy were studied. The results show that when Bi content is 0.3%, it has the most obvious deterioration effect. Bi enrichment generates component supercooling at the front end of eutectic Mg2 Si growth interface, which reduces the actual supercooling degree of the liquid phase and limits the growth speed of eutectic Mg2 Si. Eutectic Mg2 Si phase changes from coarse fiber to fine point fiber before metamorphism. The mechanical properties of the alloy are significantly improved. The tensile strength and elongation of the alloy are increased from 205 MPa and 2.8% to 240 MPa and 5.3%, respectively, increasing by 17.1% and 89.3%.